Electroforming of beryllium



United States Patent 3,278,400 ELECTROFORMING 0F BERYLLIUM Walter Strohmeier, Wurzburg, Germany, assignor to Ethyl Corporation, New York, N.Y., a corporation of Virginia No Drawing. Filed Nov. 6, 1962, Ser. No. 235,880

Claims priority, application Germany, Nov. 14, 1961,

9 Claims- (Cl. 2043) This invention relates to a novel electrolytic process for the production of beryllium metal. Specifically, this invention relates to the electrolytic separation of beryllium metal from complex compounds of organometallic beryllium compounds of the general formula MX nBeR in which R is an alkyl, cycloalkyl, alkaryl, aryl, or aralkyl group, MX is a suitable metal salt or a salt-like compound which is capable of reacting with BeR to form a complex, and n can be an integer from 1 to 6, preferably from 1 to 2.

The eelctrolytic deposition of beryllium metal from suitable salt melts has been known for some time and its feasibility technically demonstrated. However, due to the necessary use of high temperatures when working with salt melts, that type of process is not suitable to the coating of cathodes which are structurally incapable of withstanding high temperatures, viz. non-heat resistant materials.

A low temperature approach taken in the art to electrolytically deposit beryllium has been by the use of non- ;aqueous solutions or electrolytes which do not possess proton activity or in other words, those having a minimum acidity to avoid reaction with the beryllium in the system. These electrolytes comprise solutions of beryllium salts or of organornetallic compounds and organic solvents, for example ethers, nitrogen bases, or hydrocarbons. However, the above prior art approach has left much to be desired and has not proven successful for the preparation of adheernt polishable beryllium coatings. Hence, a need exists in the art for a process whereby a very adherent polishable beryllium coating can be effected at low temperatures. To approach it from another direction, a need exists in the art for a low temperature beryllium deposition process whereby non-heat resistant materials can be given a very adherent polishable beryllium coating.

An object of this invention is to provide a new electrolytic process for the production of beryllium metals. Another object of this invention is to provide beryllium coatings by a low temperature process which coatings have physical properties heretofore unobtainable in the art. Yet another object of the invention is to provide a new electrolytic beryllium plating process whereby unique beryllium coatings can be prepared on substrates heretofore not amenable to present day beryllium plating processes. These and other objects will come to light as the discussion proceeds.

These objects are accomplished by providing a process for the electrolytic separation or deposition of metallic beryllium of complex salts of organometallic beryllium compounds of the general formula 'MX nBeR wherein BeR represents a dialkyl, dicycloalkyl, dialkaryl, diaryl, or diaralkyl beryllium moiety complexed with appropriate salts of the type MX, wherein M can be a metal ion or an organic cation as, for example, tetraethylammonium or tetraisobutylammoniu-m, X is a suitable anion, e.g. fluoride, chloride, cyanide, or alkoxide, and n is an integer from 1 to 6, and preferably from 1 to 2. The electrolyte can comprise either the complex salt in a pure liquid state or a solution of the complex salt in a suitable solvent, preferably in excess BeR or in BeR wherein R can be a different hydrocarbon group, especially an alkyl or aryl group, or in a mixture of both of them.

A distinct benefit of the pure complex salts employed herein is that they generally have a melting point range of from about room temperature to about 100 C. whereby the electrolytic deposition of beryllium can be carried out at room temperature or slightly above, and at any rate at relatively low temperatures. Thus, it is now possible for the first time to beryllium coat materials which are non-heat resistant, for example artificial materials or plastics having first been coated with a conductant layer, e.g. silver.

The following examples demonstrate the unique results achieved in the practice of the present invention wherein all parts are by weight unless otherwise specified.

Example I An electrolyzing vessel comprising a glass cell having a side extension and interchangeable electrodes was set up. Both the anode and the cathode was constructed of platinum metal. The glass cell was purged with nitrogen which was employed throughout electrolysis as a protecting gas or inert atmosphere to prevent contamination of the electrolyte and effected coating.

The electrolyte employed in this instance was the potassium fluoride complex of bis(diethylberyllium) dissolved in diethylberyllium [Be(C H in a weight ratio of 1:2. The glass cell was charged with the electrolyte through the side extension whereafter a direct current was applied to the cell. During electrolysis, 1.7 volts at a current density of 0.62 amp/dm. was maintained on the cell. The temperature of the cell bath during the plating operation was 85 C. The electrolyte was vigorously stirred throughout the operation.

The experiment was terminated and inspection of the cathode revealed a shining beryllium coating.

When dicyclopentadienylberylliurn is substituted for the diethylberyllium in the procedure of Example I, similar results are obtained.

Example I] The apparatus of Example I was employed, except in this instance the cathode was constructed of copper. A very adherent gray beryllium coating which was capable of being polished was realized.

Example III The apparatus of Example I was employed, except that in this instance the cathode was constructed of copper. The electrolyte consisted of one part of the cesium fluoride complex of bis(diethylberyllium) [CsF-2Be(C H dissolved in two parts of diethylberyllium [Be(C H A voltage of 1.5 volts at a current density of 0.80 amp/ dm? was applied on the cell which was maintained at a temperature of C. A silvery, smooth beryllium coating was obtained.

Substitution of dihexylberyllium for the diethylberyllium of Example III gives similar results.

Example IV The apparatus of Example I was employed, except that in this instance a silver cathode was utilized. The electrolyte employed was the tetraethylammonium chloride complex of diethylberyllium [N(C H Cl-2Be(C H at an electrolyzing temperature of 65 C., a voltage of 1.7 volts, and a current density of 0.6 amp/dmF. Beryllium separated out on the silver cathode as a shiny coating which was highly polishable.

When diphenylberyllium, dibenzylberyllium and dixylylberyllium are individually substituted for the diethylberyllium in the procedure of Example IV, similar results are obtained.

Example V The apparatus of Example I was employed, except in this instance a sheet of silver was used as the cathode and a plate-like piece of beryllium as the anode. The electrolyte was the potassium fluoride complex of diethylberyllium [KF-2Be(C H A voltage of 1.8 volts and a current density of 0.5 amp/din. was applied upon the cell. Beryllium was dissolved at the anode while a beryllium coating was deposited on the silver cathode.

Use of the potassium cyanide complex of diethylberyllium [KCN-2Be(C H in the procedure of Example V gives similar results.

As mentioned previously and as demonstrated by the above examples, the electrolyte can comprise a pure complex salt of an alkyl, cycloalkyl, alkaryl, or aralkyl beryllium compound or the electrolyte can comprise the complex dissolved in a suitable solvent where the melting point of the complex is greater than 100 C. Thus, in the latter technique by the proper selection of the quantity relationships of the salt complex of the organoberyllium compound and the solvent, it is possible to obtain an electrolyte which is fluid at room temperature and below.

Exemplary of the organoberyllium compounds capable of complexing with the salts employed herein are: dimethylberyllium, diethylberyllium, dipropylberyllium, ditertiarybutylberyllium, dihexylberyllium, dioctylberyllium, didecylberyllium, dicyclopentadienylberyllium, dicyclohexylberyllium, diphenylberyllium, dibenzylberyllium, ditolylbery-llium, dicumenylberyllium, and the like. Those beryllium compounds containing hydrocarbon groups having up to about 8 carbon atoms per group are prefer-red since they are more readily prepared and hence offer an economic advantage. It is to be understood that the organoberyllium compounds can have mixed hydrocarbon groups, e.g. as in phenyl ethyl beryllium. The dialkylberyllium compounds containing up to about 8 carbon atoms per group are especially preferred because of their greater tendency to complex with the salts described hereinafter.

Suitable salts capable of reacting With the above organoberyllium compounds are the alkali metal salts, alkaline earth metal salts, and the tetraalkylammonium salts. The alkali metals include the metals of Group I-A of the Periodic Chart of the Elements, Fisher Scientific Company, 1959, e.g. lithium, sodium, potassium, rubidium and cesium. Generally speaking, the salts of the alkali metals of atomic numbers 19 through 55i.e. K, Rb, and Csare preferred for use in this invention. The alkali metal salts can be salts of organic or inorganic acids, the latter being generally more eflicacious. Thus, the alkali metal salts include the alkali metal halides, alkali metal alcoholates (*MOR) wherein the hydrocarbon portions contain up to and including about 18 carbon atoms; alkali pseudohalides as, for example, the alkali metal cyanides, cyanates, thiocyanates, amides, mercaptides, and the like; organic acid salts as, for example, the alkali metal salts or organic acids wherein the hydrocarbon portions have to and including about 18 carbon atoms. Typical examples of such alkali metal salts include potassium chloride, bromide, iodide, or fluoride; potassium formate, acetate, propionate, phenolate, ethylate, benzoate, isobutyrate, -and the like; including such compounds wherein lithium, sodium, rubidium, or cesium are substituted for potassium. Thus, in general, any alkali metal salt capable of complexing with the organoberyllium compounds employed pursuant to this invention can be used. However, the alkali metal halides, especially the fluorides and cyanides, comprise particularly preferred metal salts. The fluorides and cyanides of potassium, rubidium, and cesium comprise an even more preferred embodiment because of their ease of complexibility with the preferred dialkylberyllium compounds of the instant invention.

The alkaline earth metals include the metals of Group II-A of the Periodic Chart of the Elements; e.g., beryllium, magnesium, calcium, strontium, and barium. Generally speaking, the salts of the alkaline earth metals of atomic numbers 20-56-:-i.e. calcium, strontium, and barium-are preferred for use in this invention. The alkaline earth metal salts can be salts of organic or inorganic acids, the latter being generally more efficacious. Thus, the alkaline earth metal salts include the alkaline earth metal halides, alkaline earth metal alcoholates (MOR), wherein the hydrocarbon portions contain up to and including about 18 carbon atoms; alkaline earth pseudohalides as, for example, the alkaline earth metal cyanides, cyanates, thiocyanates, amides, mercaptides, and the like; organic acid salts as, for example, the alkaline earth metal salts of organic acids wherein the hydrocarbon portions have up to and including about 18 carbon atoms. Typical examples of such alkaline earth metal salts include calcium chloride, bromide, iodide, or fluoride; calcium formate, acetate, propionate, phenolate, ethylate, 'benzloate, isobutyrate, and the like; including such compounds wherein beryllium, magnesium, strontium, or barium are substituted for calcium. Thus, in general, any alkaline earth metal salt capable of complexing with the organoberyllium compounds employed pursuant to this invention can be used. However, the alkaline earth metal halides, especially the fluorides and cyanides comprise particularly preferred alkaline earth metal salts.

Of the tetraalkylam'monium salts used in this invention, the tetraalkylammonium halides, especially the fluorides and most especially the chlorides, are preferred. Examples of these particularly preferred quaternary ammonium salts include tetramethyl ammonium chloride, tetraethyl ammonium chloride, tetraethyl ammonium fluoride and the higher homologs of these compounds in which the alkyl groups are preferably lower alkyl groups containing up to about 6 carbon atoms. Other useful and preferred quaternary ammonium halide salts include tetraethyl ammonium bromide, tetramethyl ammonium iodide and similar analogous compounds.

Thus, typical of the salt complexes of the organoberyllium compounds that are electrolyzed pursuant to this invention are: potassium fluoride-diethylberyllium; potassium fluoride-bis(diethylberyllium); potassium fluoride -ditertiarybutylberyllium; cesium fluoride diethylberyllium; cesium fluoride-diphenylberyllium; calcium fluoride-'bis(diethylberyllium) strontium fluoride-bis (ditolylberyllium); tetraethyl ammonium chloride complex of diethyl'beryllium; tetraethyl ammonium chloride complex of cyclopentadienylberyllium; and the like.

Generally, the pure complex salts of the organoberyllium compounds employed in this invention have a melting point range of from about room temperature to about C. Where the melting point of a given complex is above 100 C., it is preferred to dissolve it in a solvent preparatory to its use. Thus, by a suitable selection of the quantity relationship of the complex and the solvent, it is possible to obtain an electrolyte which is fluid at temperatures less than 100 0, preferably at room temperature or below. The solvents which can be employed in the novel process of this invention are preferably organoberyllium compounds, especially the alkyl and arylberyllium compounds, which are stable under the plating conditions. Of the alkyl and arylberyllium compounds, those having up to 12 carbon atoms per organo group are preferred since they are easier to prepare in high yields and purity. It is to be noted that the organoberyllium solvent need not contain similar organo groups as that forming a part of the complex. For example, the electrolyte can comprise the potassium fluoride salt of diethylberyllium dissolved in dimethylberyllium. However, it is preferred to employ an organoberyllium solvent similar to the organoberyllium compound complexed with the salt, i.e. the potassium fluoride complex of diethylberyllium dissolved in diethylberyl-lium. This approach oflfers an economical advantage since only one type of organoberyllium compound is required in the operation.

It is .also possible to employ other solvents, such as ethers, hydrocarbons, and the like, alone or in combination with the preferred organoberyllium solvent in order to raise the quality of the galvanic coating in certain instances.

Exemplary of the solvents which can be employed in the instant invention are: dimethylberyllium, diethylberyllium, dipnopylberyllium, .di-tert-butylberyllium, dibenzylberyllium, benzene, toluene, xylene, l-ethyl-S- methyl benzene, pentane, heptane, octane, cycl'opentane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diphenylether, and the like.

The electrodes to be employed in the instant invention can be any material which has a conducting surface. The type of material employed as the cathode determines whether the disposited beryllium metal bond itself to the cathode or be readily removable therefrom. For example, where it is desired to produce a coating that is separable from the cathode, commonly referred to as electroforming where particular geometries are being produced, it is preferred to use a material such as platinum. On the other hand, where it is desired to produce a bonded or adherent coating, materials such as copper or silver are preferred. As mentioned previously, a very beneficial feature of this invention is that beryllium coatings can be effected at low temperatures which allows the use of non-heat resistant electrodes, as long as they have a conducting surface. Thus, the cathode can be any material, e.g. a plastic or synthetic material such as polyvinyl chloride or nylon, or even paper, as long as it has a conducting surface, preferably a copper or sliver surface which can be easily effected by vacuum metalizing or sputtering, or the like.

A significant feature of the present invention is that a beryllium anode can be employed whereby beryllium metal can be continually recycled through the system. Thus, it is possible to continually regenerate the electrolyte and maintain a constant concentration without experiencing extensive loss of the materials liberated upon decomposition of the beryllium compound.

During electrolysis, it is very desirable to agitate the electrolyte since this assures its intimate contact with the electrodes.

The current density and the voltage applied upon the cell during electrolysis are not critical. Their optimum values depend upon a number of factors including the nature of the cathode, decomposition of the electrolyte, and the temperature of decomposition of the organoberyllium complex salt. The optimum conditions are readily defined for a particular system.

It is extremely desirable to employ an inert atmosphere during electrolysis due to the reactivity of organoberyllium compounds with water and air. Suitable inert media are: nitrogen, hydrogen, heilum, neon, argon, krypton, xenon, gaseous aliphatic hydrocarbons, and the like.

The greatest potential growth area today for beryllium is in its pure metallic state viz. as produced pursuant to this invention. In this state, it is attractive for structural applications which take advantage of its high strength-tmweight ratio and good thermal properties, such as to form the fins on light-Weight high-temperature motors, and the like.

What is claimed is:

l. A process for the electroforming of beryllium comprising the electrolytic separation of beryllium from complex compounds of organoberyllium compounds of the general formula MX-nBeR wherein R is a hydrocarbon group selected from the group consisting of alkyl, cycloalkyl, alkaryl, arly, and aralkyl; MX is selected from the group consisting of metal salts and salt-like compounds capable of complexing with said organoberyllium compounds, and n is an integer from 1 to 6.

2. The process of claim 1 wherein said integer n is 1.

3. The process of claim 1 wherein said integer n is 2.

4. A process for the electrolytic separation of beryllium from organoberyllium compounds selected from the group consisting of alkyl beryllium and aryl beryllium compounds complexed with a salt selected from the group consisting of metal salts and salt-like compounds.

5. An electrolytic process for the preparation of beryllium coatings on a conducting surface comprising:

(a) contacting said conducting surface with an electrolyte comprising an organoberyllium compound selected from the group consisting of alkyl beryllium and aryl beryllium compounds complexed with a salt selected from the group consisting of metal salts and salt-like compounds, and

(b) passing a direct electric current through said electrolyte by way of said conducting surface whereby a beryllium coating is deposited on said conducting surface.

6. The process of claim 5 further characterized in that said electrolysis is conducted in an inert atmosphere.

7. Process of claim 6 further characterized in that said salt complexes of the organoberyllium compounds are selected from the group consisting of alkali metal, alkaline earth metal, and tetraalkyl ammonium salt complexes of dialkylberryllium compounds.

8. The process claim 6 further characterized in that said salt complex of the organoberryllium compound is an alkali metal halide salt complexed with a dialylberyllium compound.

9. The process of claim 5 further characteribed in that an anode comprising beryllium is employed whereby said electrolyte is constantly regenerated.

No references cited.

JOHN H. MACK, Primary Examiner.

T. TUFARIELLO, Assistant Examiner. 

1. A PROCESS FOR THE ELECTROFORMING OF BERYLLIUM COMPRISING THE ELECTROLYTIC SEPARATION OF BERYLLIUM FROM COMPLEX COMPOUNDS OF ORGANOBERYLLIUM COMPOUNDS OF THE GENERAL FORMULA 